In the course of manufacturing a semiconductor integrated circuit (IC), various single wafer processes such as a film forming process, an etching process, a heat treating process, a reforming process and a crystallization process are repeatedly carried out on an object to be processed, e.g., a semiconductor wafer. While executing such processes, processing gases needed for the corresponding processes, e.g., a film formation gas for the film forming process; ozone gas or the like for the reforming process; O2 gas, an inert gas such as N2 gas, or the like for the crystallization process, are respectively introduced into processing chambers.
For instance, in a single wafer processing apparatus for one by one heat treatment on semiconductor wafers, a mounting table incorporating therein, e.g., a resistance heater is installed in a processing chamber which can be evacuated. A processing gas is then introduced into the processing chamber after mounting a semiconductor wafer on the mounting table to apply various heat treatments on the wafer under given process conditions.
In performing the various heat treatments, it is required to enhance the within wafer uniformity of each heat treatment and improve the throughput thereof in order to maintain high productivity and at the same time to improve electrical characteristics of manufactured products.
In case of, for example, a reforming process for a tantalum oxide (Ta2O5) film used in a capacitor, ozone is introduced into a processing chamber which can be evacuated and the tantalum oxide film on the surface of the wafer is annealed to be reformed under the presence of O3 (ozone). By such a reforming process, a carbonic component in the tantalum oxide film is removed in the form of CO2. Accordingly, formation of a SiO2 film at an interface between a polysilicon of an underlying layer and the tantalum oxide film is facilitated, thereby improving electrical characteristics. Further, a wafer temperature and an ozone concentration are raised sufficiently enough to improve an efficiency of the reforming process.
As the competition in the manufacturing field of semiconductor ICs becomes ever fiercer recently, continuous improvement of the productivity thereof has become one of the most important keys to remain successful and profitable in the field. In the reforming process described above, however, there is an upper limit in the wafer temperature set due to heat resistance of each layer of the underlying layers formed in preceding processes. The upper limit of the wafer temperature varies depending on a type of a film of the underlying layers and is for example about 720° C. Therefore, the wafer temperature cannot be increased indefinitely in the reforming process for the sake of improving the throughput.
Further, it may be attempted to increase an ozone concentration in order to increase the throughput. Since, however, an ozone concentration is limited by an ozone generator, it is difficult to increase the ozone concentration beyond a current level.